The present invention relates to a method for detecting and tracking objects within digitized images on the basis of properties which clearly distinguish these objects from other structures appearing in the images.
The automation of processes, as well as autonomously operating systems and devices used in processing technology and systems employed by the military, require the dependable detection of objects to be manipulated, as well as of obstacles and targets, in particular highly developed partial systems contained in military systems for air defense for detecting the structure, position and direction of movement of aircraft, whose relevant data must be available extremely rapidly in order to dependably counter any threat. Because such systems are customarily equipped with active sensors, in particular surveillance and tracking radars, weapons systems have been developed which can effectively negate such sensors by using their radiation for their own target detection. Passive detection of targets is performed in the traditional way by appropriately trained personnel.
Besides the considerable outlay for training such personnel, the limited reaction speed of humans as well as the endangerment of the personnel employed at the targets which are attractive to the opponent should be mentioned as additional disadvantages.
Therefore several methods for detecting and tracking targets by extracting them from image data obtained from video and infrared cameras are already known. For example, a target can be detected within a section to be passed through an image, by comparing the statistical frequency of defined gray scale values in the section of a video image with that of the entire image. Besides the possibility of errors in the case of the presence of gray edges with corresponding gray scale value statistics extending through the entire image, there is the disadvantage that a certain minimum size of the object to be detected is required. This therefore cannot consist of only a few pixels of the entire image, so that the detection range of a video camera is even further removed from that of a surveillance radar.
The increase of the number of pixels by using special cameras also approaches a limit set by the speed with which calculations can be performed in the processors used. The first such methods are mainly reflected in the hardware, which was adapted to the specific use for achieving a high calculation speed.
Possible improvements of the method therefore resulted in an inordinate outlay because of the required adaptation of the hardware. Since implementations of such methods by providing the corresponding software for very fast and universally usable hardware have only very recently become possible at all, the special requirements for such implementable methods lie in their economical structure in respect to the volume of the required calculating operations.
It is therefore the object of the invention hereinafter described to assure the detection and tracking of targets in digitized images with a minimal outlay for calculating operations, while avoiding the described disadvantages of the prior art.
Methods in accordance with the prior art use a relatively large area for detecting gray scale values and similar characteristics in order to extract a target from an image. But the method in accordance with the invention uses only certain elements from the total amount of image pixels containing the target. These are moreover obtained by transformations of the actual amount of target pixels and their additional reduction to essential pixels. A characteristic pattern of the target obtained by this is employed in subsequent images for tracking by correlating it with all the pixels of an image section to be searched, wherein the correlation maximum indicates the new position of the target. The characteristic pattern of the target is furthermore continuously updated by means of an integration process in order to take into account changes in the target profile, for example if an aircraft rotates around its axis in the course of making turns.
A considerable advantage of the method in accordance with the invention lies in minimizing the calculation efforts required for detecting a target, establishing its pattern and tracking it, which consists of minimizing the number of pixels to be processed.
A further advantage is the result of the high degree of dynamics of the system in regard to the extension of the objects to be detected. Therefore it is possible by means of the described method steps to reduce an extended object to a few significant image pixels. However, since only a few pixels are required for identifying a target, it is also possible by means of the method of the invention to detect and track targets which only include a few unprocessed pixels. Therefore the possibility also exists of detecting and tracking guided missiles and drones without the employment of active sensors.
Further details, characteristics and advantages of the invention ensue not only from the claims and the characteristics to be taken from them, either by themselves and/or in combination, but also from the following description of preferred exemplary embodiments.